.. _path: **** PATH **** :abbr:`PATH` is a daemon that handles the installation and deletion of Segment Routing (SR) Policies. Based on MPLS (This means that your OS of choice must support MPLS), SR add a stack of MPLS labels to ingress packets so these packets are egress through the desired path. .. image:: images/pathd_general.png The SR policies and Segment Lists can be configured either locally by means of vtysh or centralized based on a SDN controller (ODL, Cisco, ...) communicating using the PCEP protocol (:rfc:`5440`). .. _starting-path: Configuration ============= Explicit Segment Lists ---------------------- This is the simplest way of configuration, no remote PCE is necessary. In order to create a config that match the graphics used in this documentation, we will create a segment list (SL) called SL1 with an element for each hop and that element will be assigned a MPLS label. Then the SL1 will be used in the policy ``example1``, please note also the preference as in the case of multiple segment list it will be used with the criteria of bigger number more preference. Let see now the final configuration that match the graphics shown above. .. code-block:: frr segment-routing traffic-eng segment-list SL1 index 10 mpls label 16001 index 20 mpls label 16002 ! policy color 1 endpoint 192.0.2.4 name example1 binding-sid 1111 candidate-path preference 100 name CP1 explicit segment-list SL1 Explicit Segment Lists and Traffic Engineering Database (TED) ------------------------------------------------------------- Sometimes is difficult to know the values of MPLS labels (adjacency changes,...). Based on the support of IS-IS or OSPF we can activate TED support what will allow pathd to resolve MPLS based in different types of segments (:rfc: `draft-ietf-spring-segment-routing-policy-07`). The supported types are Type C (prefix and local interface), Type E (prefix and algorithm), Type F (a pair of IP's). So the configuration would change to this .. code-block:: frr segment-routing traffic-eng mpls-te on mpls-te import ospfv2 segment-list SL1 index 10 nai prefix 10.1.2.1/32 iface 1 index 20 nai adjacency 10.1.20.1 10.1.20.2 ! policy color 1 endpoint 192.0.2.4 name example1 binding-sid 1111 candidate-path preference 100 name CP1 explicit segment-list SL1 In this case no MPLS are provided but the pathd TED support will resolve the configuration provided to corresponding MPLS labels. .. note:: Please note the ``mpls-te`` configuration added that activate the TED support and points to ``ospfv2`` so the ospfv2 (:ref:`ospf-traffic-engineering`) daemon must be also running and configure to export TED information. .. note:: It would be the same for isis (:ref:`isis-traffic-engineering`) but in the moment of writting it's not fully tested. Dynamic Segment Lists --------------------- One of the useful options to configure is the creation of policies with the dynamic option. In this case based on a given endpoint the SL will be ,first calculated, and then sended by means of PCEP protocol by the configured PCE. .. code-block:: frr traffic-eng ! pcep ! pce PCE1 address ip 192.0.2.10 ! pcc peer PCE1 precedence 10 ! policy color 1 endpoint 192.0.2.4 name example binding-sid 1111 candidate-path preference 100 name CP2 dynamic .. note:: Please note the configuration for the remote pce which allows pathd to connect to the given PCE and act as a PCC (PCEP Client) .. note:: If the TED support feature is active, the data obtained from PCE will be validated, so in a SL from PCEP/PCE the IP and MPLS will be checked against local TED obtained and built from the igp configured in that case. .. image:: images/pathd_config.png Pce Initiated ------------- We can step forward in the use of our controller not only by asking to calculate paths to an endpoint but also to create the whole policies in the controller and obtain those by means of the PCEP protocol. .. code-block:: frr traffic-eng ! pcep ! pce PCE1 address ip 192.0.2.10 pce-initiated ! pce PCE2 address ip 192.0.2.9 pce-initiated ! pcc peer PCE1 precedence 10 peer PCE2 precedence 20 ! .. note:: Now there is no locally created policies in the config as they will be obtain from the configured pce. Please check command :clicmd:`show sr-te policy` in ``vtysh`` to see the obtained policies. .. note:: Another interesting command is :clicmd:`show mpls table` to check the installed mpls configuration based in those obtained policies. .. note:: SR Policies could be a mix of local, remote obtained from PCE and delegated to a PCE (but while testing Pce Initiated with Cisco PCE, happens that controller sends PCE initiated delete commands to delete the locally created configuration related to that PCE). .. image:: images/pathd_initiated_multi.png Starting ============= Default configuration file for *pathd* is :file:`pathd.conf`. The typical location of :file:`pathd.conf` is |INSTALL_PREFIX_ETC|/pathd.conf. If the user is using integrated config, then :file:`pathd.conf` need not be present and the :file:`frr.conf` is read instead. .. program:: pathd :abbr:`PATH` supports all the common FRR daemon start options which are documented elsewhere. PCEP Support ============ A pceplib is included in the frr source tree and build by default. To start pathd with pcep support the extra parameter `-M pathd_pcep` should be passed to the pathd daemon. An example of command line with pcep module could be this .. code-block:: frr pathd -u root -g root -f pathd.conf -z /tmp/zebra-demo1.sock --vty_socket=/var/run/demo1.vty -i /tmp/pathd-demo1.pid -M frr/modules/pathd_pcep.so --log file:/tmp/kk.txt Pathd Configuration =================== Example: .. code-block:: frr debug pathd pcep basic segment-routing traffic-eng mpls-te on mpls-te import ospfv2 segment-list SL1 index 10 mpls label 16010 index 20 mpls label 16030 ! segment-list SL2 index 10 nai prefix 10.1.2.1/32 iface 1 index 20 nai adjacency 10.1.20.1 10.1.20.2 index 30 nai prefix 10.10.10.5/32 algorithm 0 index 40 mpls label 18001 ! policy color 1 endpoint 192.0.2.1 name default binding-sid 4000 candidate-path preference 100 name CP1 explicit segment-list SL1 candidate-path preference 200 name CP2 dynamic affinity include-any 0x000000FF bandwidth 100000 metric bound msd 16 required metric te 10 objective-function mcp required ! pcep pce-config GROUP1 source-address 192.0.2.1 tcp-md5-auth secret timer keep-alive 30 ! pce PCE1 config GROUP1 address ip 192.0.2.10 ! pce PCE2 config GROUP1 address ip 192.0.2.9 ! pcc peer PCE1 precedence 10 peer PCE2 precedence 20 ! ! ! ! .. _path-commands: Configuration Commands ---------------------- .. clicmd:: segment-routing Configure segment routing. .. clicmd:: traffic-eng Configure segment routing traffic engineering. .. clicmd:: mpls-te Activate/Deactivate use of internal Traffic Engineering Database .. clicmd:: mpls-te import Load data from the selected igp .. clicmd:: segment-list NAME Delete or start a segment list definition. .. clicmd:: index INDEX mpls label LABEL .. clicmd:: index INDEX nai adjacency A.B.C.D A.B.C.D .. clicmd:: index INDEX nai prefix A.B.C.D/M algorithm <0|1> .. clicmd:: index INDEX nai prefix A.B.C.D/M iface (0-65535) Delete or specify a segment in a segment list definition. .. clicmd:: policy color COLOR endpoint ENDPOINT Delete or start a policy definition. .. clicmd:: name NAME Specify the policy name. .. clicmd:: binding-sid LABEL Specify the policy SID. .. clicmd:: candidate-path preference PREFERENCE name NAME explicit segment-list SEGMENT-LIST-NAME Delete or define an explicit candidate path. .. clicmd:: candidate-path preference PREFERENCE name NAME dynamic Delete or start a dynamic candidate path definition. .. clicmd:: affinity BITPATTERN Delete or specify an affinity constraint for a dynamic candidate path. .. clicmd:: bandwidth BANDWIDTH [required] Delete or specify a bandwidth constraint for a dynamic candidate path. .. clicmd:: metric [bound] METRIC VALUE [required] Delete or specify a metric constraint for a dynamic candidate path. The possible metrics are: - igp: IGP metric - te: TE metric - hc: Hop Counts - abc: Aggregate bandwidth consumption - mll: Load of the most loaded link - igp: Cumulative IGP cost - cte: Cumulative TE cost - igp: P2MP IGP metric - pte: P2MP TE metric - phc: P2MP hop count metric - msd: Segment-ID (SID) Depth - pd: Path Delay metric - pdv: Path Delay Variation metric - pl: Path Loss metric - ppd: P2MP Path Delay metric - pdv: P2MP Path Delay variation metric - ppl: P2MP Path Loss metric - nap: Number of adaptations on a path - nlp: Number of layers on a path - dc: Domain Count metric - bnc: Border Node Count metric .. clicmd:: objective-function OBJFUN1 [required] Delete or specify a PCEP objective function constraint for a dynamic candidate path. The possible functions are: - mcp: Minimum Cost Path [RFC5541] - mlp: Minimum Load Path [RFC5541] - mbp: Maximum residual Bandwidth Path [RFC5541] - mbc: Minimize aggregate Bandwidth Consumption [RFC5541] - mll: Minimize the Load of the most loaded Link [RFC5541] - mcc: Minimize the Cumulative Cost of a set of paths [RFC5541] - spt: Shortest Path Tree [RFC8306] - mct: Minimum Cost Tree [RFC8306] - mplp: Minimum Packet Loss Path [RFC8233] - mup: Maximum Under-Utilized Path [RFC8233] - mrup: Maximum Reserved Under-Utilized Path [RFC8233] - mtd: Minimize the number of Transit Domains [RFC8685] - mbn: Minimize the number of Border Nodes [RFC8685] - mctd: Minimize the number of Common Transit Domains [RFC8685] - msl: Minimize the number of Shared Links [RFC8800] - mss: Minimize the number of Shared SRLGs [RFC8800] - msn: Minimize the number of Shared Nodes [RFC8800] .. clicmd:: debug pathd pcep [basic|path|message|pceplib] Enable or disable debugging for the pcep module: - basic: Enable basic PCEP logging - path: Log the path structures - message: Log the PCEP messages - pceplib: Enable pceplib logging .. clicmd:: pcep Configure PCEP support. .. clicmd:: pce-config NAME Define a shared PCE configuration that can be used in multiple PCE declarations. .. clicmd:: pce NAME Define or delete a PCE definition. .. clicmd:: config WORD Select a shared configuration. If not defined, the default configuration will be used. .. clicmd:: address [port (1024-65535)] Define the address and port of the PCE. If not specified, the port is the standard PCEP port 4189. This should be specified in the PCC peer definition. .. clicmd:: source-address [ip A.B.C.D | ipv6 X:X::X:X] [port PORT] Define the address and/or port of the PCC as seen by the PCE. This can be used in a configuration group or a PCC peer declaration. If not specified, the source address will be the router identifier selected by zebra, and the port will be the standard PCEP port 4189. This can be specified in either the PCC peer definition or in a configuration group. .. clicmd:: tcp-md5-auth WORD Enable TCP MD5 security with the given secret. This can be specified in either the PCC peer definition or in a configuration group. .. clicmd:: sr-draft07 Specify if a PCE only support segment routing draft 7, this flag will limit the PCC behavior to this draft. This can be specified in either the PCC peer definition or in a configuration group. .. clicmd:: pce-initiated Specify if PCE-initiated LSP should be allowed for this PCE. This can be specified in either the PCC peer definition or in a configuration group. .. clicmd:: timer [keep-alive (1-63)] [min-peer-keep-alive (1-255)] [max-peer-keep-alive (1-255)] [dead-timer (4-255)] [min-peer-dead-timer (4-255)] [max-peer-dead-timer (4-255)] [pcep-request (1-120)] [session-timeout-interval (1-120)] [delegation-timeout (1-60)] Specify the PCEP timers. This can be specified in either the PCC peer definition or in a configuration group. .. clicmd:: pcc Disable or start the definition of a PCC. .. clicmd:: msd (1-32) Specify the maximum SID depth in a PCC definition. .. clicmd:: peer WORD [precedence (1-255)] Specify a peer and its precedence in a PCC definition. Introspection Commands ---------------------- .. clicmd:: show sr-te policy [detail] Display the segment routing policies. .. code-block:: frr router# show sr-te policy Endpoint Color Name BSID Status ------------------------------------------ 192.0.2.1 1 default 4000 Active .. code-block:: frr router# show sr-te policy detail Endpoint: 192.0.2.1 Color: 1 Name: LOW_DELAY BSID: 4000 Status: Active Preference: 100 Name: cand1 Type: explicit Segment-List: sl1 Protocol-Origin: Local * Preference: 200 Name: cand1 Type: dynamic Segment-List: 32453452 Protocol-Origin: PCEP The asterisk (*) marks the best, e.g. active, candidate path. Note that for segment-lists which are retrieved via PCEP a random number based name is generated. .. clicmd:: show sr-te pcep counters Display the counters from pceplib. .. clicmd:: show sr-te pcep pce-config [NAME] Display a shared configuration. if no name is specified, the default configuration will be displayed. .. clicmd:: show sr-te pcep pcc Display PCC information. .. clicmd:: show sr-te pcep session [NAME] Display the information of a PCEP session, if not name is specified all the sessions will be displayed. Utility Commands ---------------- .. clicmd:: clear sr-te pcep session [NAME] Reset the pcep session by disconnecting from the PCE and performing the normal reconnection process. No configuration is changed. Usage with BGP route-maps ========================= It is possible to steer traffic 'into' a segment routing policy for routes learned through BGP using route-maps: .. code-block:: frr route-map SET_SR_POLICY permit 10 set sr-te color 1 ! router bgp 1 bgp router-id 192.0.2.2 neighbor 192.0.2.1 remote-as 1 neighbor 192.0.2.1 update-source lo ! address-family ipv4 unicast neighbor 192.0.2.1 next-hop-self neighbor 192.0.2.1 route-map SET_SR_POLICY in redistribute static exit-address-family ! ! In this case, the SR Policy with color `1` and endpoint `192.0.2.1` is selected. Sample configuration ==================== .. code-block:: frr ! Default pathd configuration sample ! password frr log stdout segment-routing traffic-eng segment-list test1 index 10 mpls label 123 index 20 mpls label 456 ! segment-list test2 index 10 mpls label 321 index 20 mpls label 654 ! policy color 1 endpoint 192.0.2.1 name one binding-sid 100 candidate-path preference 100 name test1 explicit segment-list test1 candidate-path preference 200 name test2 explicit segment-list test2 ! policy color 2 endpoint 192.0.2.2 name two binding-sid 101 candidate-path preference 100 name def explicit segment-list test2 candidate-path preference 200 name dyn dynamic bandwidth 12345 metric bound abc 16 required metric te 10 ! ! pcep pcc-peer PCE1 address ip 127.0.0.1 sr-draft07 ! pcc peer PCE1 ! ! !